During operation of a system that includes virtual machines on which plural processes operate, there is a case that, for example, processing requests to part of the plural processes increase and processing loads of those virtual machines will increase.
In automated scale-out, when an excessive load on any one of virtual machines included in the system is detected, a processing load may be dispersed by adding a new virtual machine that has all functions the same as those of the virtual machine for which the excessive load was detected.
In a certain patent reference, a technique to instantiate a new image of a virtual server when an idle time of the CPU (Central Processing Unit) of the virtual server drops below a reference value is disclosed. Moreover, in the same patent reference, a technique to instantiate a virtual server by using an image that includes software set is also disclosed.
In this way, by preparing an image that corresponds to a virtual machine whose load potentially becomes excessive, and then adding a new virtual machine by using that image when the load of the virtual machine actually becomes excessive, the new virtual machine takes on the same functions as those of the virtual machine whose load became excessive. As a result, part of the processing requests will be treated in the new virtual machine and the excessive load will be reduced.
When this happens, resources are assigned to software installed in the new virtual machine. Therefore, when many kinds of software are included in the image prepared in advance, many resources are required for the new virtual machine. Moreover, in the case that the software does not contribute to dispersion of the processing load, the resources assigned to the software are wasted.
Patent Document 1: Japanese National Publication of International Patent Application No. 2011-523472
Patent Document 2: Japanese Laid-open Patent Publication No. 2012-208781
Patent Document 3: Japanese National Publication of International Patent Application No. 2003-507817
In other words, in conventional arts, there is no technique to enable to reduce consumption of resources in a virtual machine newly deployed.